We carried out the basic research for the preparation of artificial nucleus pulposus using the gelatin which the collagen was solubilized.Gelatin has no gel strength as nucleus pulposus, because gelatin solution is in liquid state near die body temperature. The crosslinking agent (the potassium alum) was added to. the gelatin solution so that the gelatin may gel near the body temperature. The gelatin gel was preserved at 40ﾟC and the gel strength Was measured. It was proven that the gel strength decreased when the preservation period is lengthened, and that the gel resolves. Antiseptic was used in order to prevent the decomposition. Though the diminution rate of gel strength slowed down, when antiseptics were added, die decrease in the gel strength could not be prevented. Then, the experiment was carried out using other crosslinking agents. The gel strength in addition of crosslinking agent, such as A or B or C, rose than potassium alum and the period for the decrease in the gel strength was lengthened. However, the gel strength decreased when die gel was preserved for a long time at 40ﾟC.From the above result, it was proven that the gel saving for a long time at 40ﾟC was difficult.In the process of this research, we developed a new method for controlling the molecular weight distribution of die gelatin. We developed a method for preparation the gelatin in which in alpha and beta components are rich ; pressurizing the gelatin solution and jetting it at high speed so that die high molecular weight component in it may cleave.In the future, die condition near in the organism being variously devised, and using the gelatin which controlled die molecular weight distribution, the research of artificial nucleus pulposus using the gelatin whose molecular weight distribution is controlled will be kept.